[UX] Wait 0.5s before showing "searching for" dialog (#7012)

Fixes <https://github.com/koreader/koreader/issues/3030>.

Cross-ref to <https://github.com/koreader/koreader/pull/6998>.

frontend/apps/reader/modules/readerdictionary.lua

@@ -819,10 +819,11 @@ function ReaderDictionary:stardictLookup(word, dict_names, fuzzy_search, box, li
     end
 
     if fuzzy_search then
-        self:showLookupInfo(word)
+        UIManager:scheduleIn(0.5, self.showLookupInfo, self, word)
     end
 
     local results = self:startSdcv(word, dict_names, fuzzy_search)
+    UIManager:unschedule(self.showLookupInfo)
     self:showDict(word, tidyMarkup(results), box, link)
 end